Financial Assets Measured at Fair Value on a Recurring Basis (Detail) (Fair Value, Measurements, Recurring, USD $) In Thousands	Jun. 30, 2011		Sep. 30, 2010
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total	$ 207,724		$ 155,527
Active Markets for Identical Instruments (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total	90,131		86,912
Active Markets for Identical Instruments (Level 1) | Cash equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	85,285	[1]	82,545	[1]
Active Markets for Identical Instruments (Level 1) | Marketable securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities available-for-sale	4,846	[2]	4,367	[2]
Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total	117,593		68,615
Significant Other Observable Inputs (Level 2) | U.S. corporate debt
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities available-for-sale	21,996	[3]	2,981	[3]
Significant Other Observable Inputs (Level 2) | U.S. government obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities available-for-sale	95,597	[3]	39,452	[3]
Significant Other Observable Inputs (Level 2) | Non U.S. corporate debt
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities available-for-sale			17,267	[3]
Significant Other Observable Inputs (Level 2) | U.S. municipal obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities available-for-sale			8,915	[3]
Cash equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	85,285	[1]	82,545	[1]
U.S. corporate debt
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities available-for-sale	21,996	[3]	2,981	[3]
U.S. government obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities available-for-sale	95,597	[3]	39,452	[3]
Marketable securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities available-for-sale	4,846	[2]	4,367	[2]
Non U.S. corporate debt
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities available-for-sale			17,267	[3]
U.S. municipal obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities available-for-sale			$ 8,915	[3]

[1] Included in cash and cash equivalents on our balance sheet at June 30, 2011 and September 30, 2010. Not included in this table are cash deposits of $55.6 million and $63.7 million at June 30, 2011 and September 30, 2010, respectively.

[2] Represents securities held under a supplemental retirement and savings plan for certain officers and senior management employees, which are distributed upon termination or retirement of the employees. Included in long-term marketable securities on our balance sheet at June 30, 2011 and September 30, 2010.

[3] Included in current marketable securities on our balance sheet at June 30, 2011 and September 30, 2010.